This invention relates to vehicle emissions control, and particularly to a refueling vapor recovery system designed to capture, store, and subsequently purge the fuel vapors that are displaced and generated during a typical vehicle refueling operation. More particularly, this invention relates to a vent assembly that is mounted in an outlet formed in a fuel tank wall and includes a housing containing a roll-over valve and a vapor recovery valve.
Polluting emissions are released into the atmosphere during each and every motor vehicle refueling activity. Typically, removal of a fuel cap permits pressurized fuel vapors present within the vehicle fuel system to escape to the atmosphere. In view of the frequency of vehicle refueling activities, it will be appreciated that a significant quantity of otherwise combustible fuel is lost to the atmosphere each time a vehicle is refueled.
New fuel vapors are generated during refueling due to splash and agitation of the dispensed fuel, as well as from potential temperature differences between the fuel tank and the dispensed fuel. In addition, as the liquid fuel dispensed at the pump fills the vehicle fuel tank, fuel vapors that are present in the tank and generated during refueling are displaced by liquid fuel. These displaced fuel vapors are moved out of the fuel tank vapor space by the displacing action of the liquid fuel. In conventional vehicle fuel systems, these displaced vapors are released directly into the atmosphere via the fuel tank filler neck and are a contributing factor to air pollution.
One object of the present invention is to provide an emissions control system for advantageously capturing fuel vapors normally discharged during a vehicle refueling activity so as to reduce waste of fuel energy resources, assist in reducing the level of air pollution, and avoid the shortcomings of conventional vehicle fuel systems.
Another object of the present invention is to provide a fuel vapor recovery system that conforms to all government environmental and safety regulations regarding evaporative and refueling emissions, exhaust emissions, and vehicle impact, and that also satisfies customer-perceived vehicle functions such as drivability, ease of refueling, and control of fuel vapor odor.
Yet another object of the present invention is to provide a compact vapor recovery valve assembly having a roll-over valve incorporated therein that is conveniently mountable in a single outlet formed in a fuel tank wall separate from the filler neck so as to consolidate substantially all of the fuel vapor valving associated with the vapor recovery system in a central, accessible location on the fuel tank.
Another object of the present invention is to provide a venting module in an outlet formed in a fuel tank wall of a vehicle that is suitable for use in a fuel vapor recovery system and also constructed to reduce the likelihood of liquid fuel spillage from the fuel tank during vehicle rollover or the like. Desirably, one valve in the venting module is opened automatically during vehicle refueling by vacuum or other remote control means to permit pressurized fuel vapor in the fuel tank to be exhausted to a fuel vapor treatment site such as a charcoal canister. In addition, another valve in the venting module is desirably closed automatically during vehicle rollover or the like by gravity or other rollover sensing means to reduce likelihood of escape of liquid fuel from the fuel tank through the venting module itself.
Still another object of the present invention is to provide buoyant means for blocking the flow of liquid fuel through a vapor recovery valve assembly mounted in an outlet formed in a fuel tank wall when the fuel tank has been filled to near capacity so as to reduce the likelihood that liquid fuel will be discharged through the valve assembly due to high fuel levels or to splashing of the liquid fuel during filling of the fuel tank.
According to the present invention, a fuel vapor recovery system suitable for use in a vehicle includes means for dividing an outlet formed in a vehicle fuel tank into separate first and second fuel vapor flow ports. Each of the first and second ports exhaust pressurized fuel vapor from the fuel tank unless blocked by valve means. Vapor delivery means is provided for conducting fuel vapor from the first and second ports to a fuel vapor treatment site such as a charcoal canister or other vapor condenser positioned elsewhere in the vehicle. The fuel vapor recovery system advantageously processes fuel vapor discharged from the fuel tank through the outlet formed in the fuel tank wall to reduce environmentally hazardous emissions without discharging unprocessed fuel vapor to the atmosphere during refueling.
The fuel vapor recovery system further includes roll-over valve means and vapor recovery valve means. The roll-over valve means selectively blocks the flow of fuel vapors through the first fuel vapor port during vehicle rollover, thereby preventing liquid fuel from leaking out of the vehicle fuel tank into the vapor delivery means through the first port. The vapor recovery valve means selectively regulates the flow of fuel vapors through the second fuel vapor flow port. The vapor recovery valve means controls the discharge of pressurized fuel vapor from the fuel tank to the vapor delivery means through the second port.
Illustratively, the outlet formed in the fuel tank wall is situated away from the fuel tank filler neck. The likelihood that liquid fuel will escape from the fuel tank through either of the first and second ports is significantly reduced by forming this separate outlet in the top wall of the fuel tank. The roll-over and vapor recovery valve means act to control flow of fuel vapor and liquid fuel through the separate top fuel tank outlet. In addition, partition means is provided in the fuel tank filler neck for sealing a fuel dispensing nozzle to the filler neck during refueling. The partition means prevents loss of fuel vapor to the atmosphere through the filler neck during operation of the vapor recovery valve means in the separate fuel tank outlet.
In preferred embodiments, the fuel vapor recovery system includes a hollow venting module housing mounted in the outlet formed in the fuel tank wall. The interior region of the housing is divided by a partition into a first chamber inside the fuel tank for containing the roll-over valve means and a second chamber outside the fuel tank for containing the vapor recovery valve means. The hollow housing includes an inlet for admitting fuel vapor in the fuel tank into the first chamber and an outlet for exhausting fuel vapor in the second chamber to a point of use. The first and second chambers are interconnected by means of an aperture formed in the partition.
The roll over valve means incudes a nozzle for discharging fuel vapors from the first chamber into the second chamber and a valve piece for closing the nozzle. The distal end of the nozzle has a discharge opening. The valve piece is movable into the nozzle in response to tilting the roll-over valve means during a vehicle rollover or the like to block the flow of the fuel vapors through the first port during vehicle roll over conditions.
The discharge opening of the nozzle provides the first port in the fuel tank outlet. The nozzle extends into the partition aperture in spaced relation to the inwardly-facing rim of the partition aperture to define an annular space therebetween providing the second port in the fuel tank outlet. Thus, the second port is of annular shape and surrounds the generally circular first port.
The vapor recovery valve means includes a valve member in the second chamber and spring means for biasing the valve member against the partition to a position closing the second port. The valve member has a central aperture and is positioned in the second chamber to place the central aperture in alignment with the discharge opening of the nozzle when the second port is closed by the valve member so that fuel vapor can still be exhausted from the fuel tank via the first port. Of course, exhaust of fuel vapor through the first port will be blocked by the roll-over valve piece during vehicle rollover substantially to prevent the loss of liquid fuel in the fuel tank through the first port in the fuel tank outlet. In addition, the spring constant of the spring means is selected to ensure that the valve member will remain biased in its closing position substantially to prevent fuel loss through the second port during vehicle rollover.
The vapor recovery means further includes actuation means for selectively moving the valve member against the spring means to open the second port during vehicle refueling. This permits fuel vapor discharged from the fuel tank during each refueling activity to be conducted to the canister for liquid fuel recovery treatment therein prior to being discharged to the atmosphere. Illustratively, the actuation means is a vacuum system including a diaphram, a stem connecting the diaphram to the valve member, and means for applying a vacuum to the diaphram to move the valve member within the housing between a second port-closing and a second port-opening position. Preferably, the actuation means includes means for sensing the beginning of a vehicle refueling activity cycle.
A fuel cap is provided for closing and sealing the mouth of the fuel tank filler neck. In preferred embodiments, sufficient loosening of the fuel cap on the filler neck actuates the refueling control valve via the vacuum system to initiate a vapor recovery sequence without breaking the vapor seal provided by the fuel cap or otherwise permitting untreated fuel vapor to be discharged directly into the atmosphere. The sensing means includes a control pad movable relative to the filler neck between positions in close proximity to the mouth of the filler neck. Illustratively, the control pad is spring-biased against the fuel cap whenever the fuel cap is mounted on the filler neck.
Also in preferred embodiments, float means is provided for selectively closing the inlet in the first chamber in response to accumulation of liquid fuel in the fuel tank in excess of a predetermined amount. The float means floats in liquid fuel in the tank and rises to its inlet-closing position as the liquid fuel level in the tank increases. The risk of discharge of liquid fuel through either the first or the second port is significantly reduced by the float means since liquid fuel is generally unable to enter the first chamber via the inlet at high liquid fuel levels of the fuel tank .
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.